Enteric coating



latented Feb. 6, 1951 ENTERIC COATING Harold A. Clymer, Southampton, and Donald R. MacDonncll, Wayne, Pa., assignors to Smith, Kline & French Laboratories, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application April 24, 1948, Serial No. 23,127

6 Claims.

This invention relates to an improved enteric coating for medicaments.

As is well known, the desiderata of enteric coating are to protect an orally ingested medicament against release in the stomach, under the action of the fluids of the stomach or agitation therein, and, at the same time, allow release of the medicament in the intestines, under the action of the fluids therein, before elimination from the body. Such an enteric coating is said to have integrity in the stomach.

Heretofore various enteric coatings comprising various materials have been suggested and used. However, the best of the prior enteric coatings have not proved satisfactory for various reasons, chief among which are that the coating material where resistant to attack by the fluids of the stomach and, at the same time, soluble in the fluids of the intestines, is permeable by the fluids of the stomach with the result that the medicament if soluble in the stomach fluids is largely leached out through the coating; and where the material is resistant to attack and impermeable by the fluids of the stomach, it becomes ruptured by the agitation in the stomach, thus allowing l the stomach fluids to attack the medicament.

By way of illustration, heretofore an enteric coating comprising a cellulose derivative containing free carboxyl groups substantially insoluble in th fluids of the stomach and soluble in the intestinal fluids, as, for example, cellulose acetate phthalate (see U. S. Patent No. 2,196,768) has been widely used, but has proved unsatisfactory where the medicament is soluble in the stomach fluids since coatings thereof on a medicament, of a thickness to permit release of the medicament in the intestines before elimination, are permeable bythe fluids of the stomach, which are thus enabled to leach out or extract the medicament variously to a greater or less extent depending upon the conditions existing in the stomach at the time of ingestion, the period of retention in the stomach and the solubility of the medication in the stomach juices.

As further illustrative, a heretofore used enteric coating ha comprised a wax, as, for example, beeswax. However, such a, coating of a thickness permitting release of the medicament in the intestines before elimination has proved unsatisfactory, since it becomes ruptured under agitation in the stomach and permits direct attack upon the medicament by the fluids of the stomach.

Now in accordance with this invention, it has been found that an enteric coating having integrity in the fluids of the stomach which will 2 readily release a medicament in the intestines and which is substantially not soluble or dispersible in and impermeable by the fluids of the stomach and proof against rupture by agitation in the stomach, is provided by double coating, as for example, by first coating a medicament, in pellet, tablet, capsule, granular, or other form, with a cellulose derivative containing free carboxyl groups and which i substantially insoluble in stomach fluids and soluble in intestinal fluids, and then overcoating with a non-toxic wax.

The wax coating may be of a first type which will be dissipated under the action of intestinal fluids or of a second type which will be dissipated only under abrasive action in the gastro-intestinal tract.

The enteric coating according to this invention has been found to provide effective protection of the medicament in the stomach. When the wax coating is the outer coating, it acts to prevent penetration of the inner coating by stomach fluids and the inner coating acts to support and stay the outer wax coat against rupture from agitation in the stomach. When the wax coating is the inner of the two coatings, it acts to prevent stomach fluids which have permeated the outer coating from reaching the medicament while the outer coating protects the wax coating from being ruptured. Thus the two coatings interact uniquely to effectivel protect the medicament in the stomach.

In proceeding for the preparation of enteric coated medicaments according to this invention, while any of the several compounds disclosed by U. S. Patent No. 2,196,768, the disclosure of which is made a part hereof, may be used for the function of one of the coats, it is preferred to use cellulose acetate phthalate. l/Vhen thi first coat is; the inner coat, it may be, for example, but without limitation 2%5% of the weight of the tablet or other form of the medicament and when used as the outer coat it may be, for example, without limitation 5%10% of the weight of the tablet. or other form of the medicament.

When the Wax coat is to be of the first type which will be dissipated under the action of intestinal fluids, it may be formed by the use of any wax which is substantially not soluble or dispersible in the stomach fluids and rapidly soluble or dispersible in the intestinal fluids, as, for example, a glyceryl ester or a diglycol ester of a higher fatty acid such as glyceryl monostearate, diglycol stearate, diethylene glycol monostearate, glyceryl myristate, or the like, alone or in admixture with a wax which is insoluble and not dispersible in the gastro-intestinal tract such as. for example, beeswax, Japan wax, paraffin, carnauba wax, bayberry wax, hydrocarbon waxes,

be, for example, 1%-4% of the weight came:

tablet, or other form of the medicament.

When the wax coat of the aforementioned first type is formed by the use of a wax which is sub stantially not soluble or dispersible in the stomach fluids and rapidly soluble or dispersible' m the intestinal fluids admixed with a wax which is insoluble and notdispersi-ble in the gastrm When. the wax coat is tabs of the aforementioned second type, the coat is formed by theme of'a'wax'whi'ch'is insoluble and not dispersibl'e in the gastro-intestinal tract, such as, forexample, those exemplified above. W hen: such a coatingis used, it will'preferably bell%-=2z%= by weight of the tablet or other form of the medicament and willin no casebe more than 5% or less than 0.5% by-weightof the tablet orother. form of the medicament.

Weintend to include within the scopeoaths term wax when used-herein and in the claims appended hereto all of the above menti oned waxes and mixtures thereof.

All. or" the several coatings maybe formed successively' through the medium' of solutions orv dope-s" comprising the respective substances,-byj conventional procedure and withthe use of conventional apparatus. Each coatingthroughoutr its extent will, of course, be of substantially uniform thickness.

The following examples are more specifieally illustrative of this invention:

Example 1 A tablet containing 5 mg. amphetamine'sulfate' is" coated," in any usual. manner, with cellulose acetate phthalate', theweight'of the coating being I about 5% of'the weight of the tablet. The thuscoated tablet is then overcoated with a mixture comprising '75 parts by weight ofglycer'yl mono,-

stearate andf'2-5' parts by. weight of beeswax; the

weight of the coatingbein'g about 2% of the weight cf'the tablet.

Example 2 tablet;

4 Example 3 A tablet containing 200 mg. of theophylline ethylenediamine is coated, in any conventional manner, with cellulose acetate phthalate, the weight of the coating being about 10% of ,the weight of the tablet. Th'thus coatedtablet is then ovei'cdated with a mixture comprising 85 parts by weight of glyceryl myristate and 15 parts by--weight of Japan wax, the weight of the coating-being-about 3% of the weight of the tablet.

Example 4 A' tablet' containing 5 mg. amphetamine sulfateis' coated; in'an'y conventional manner, with cellulose acetate phthalate, the weight of the coatingibeing ab'out 9% of the weight of the The thus coated tablet is then over-coated with a mixture comprising parts by weight of diethyleneglycol monostearate and 20 parts by weight of bayberry wax, the weight of the coating' beingaboutab of the weight 'ofthe tablet.

Emam'ple 5' A: tablet containingzoo'mg; of theophyll'ine" ethylenediamine is coated, in any'converitional manner, with cellulose acetate phthala'te; thewei ht of} the coating being about 10% of the weight offthe tablet. The thuscoated tableti is" then di e'rcoated with a mixturecomprising'w parts by weight of diglycolste'arateand'B'O parts by weight of parafiin, the weight of'thecoating" bei'ng"a oout 3% of the 'weight ofthe tablet.

Eita'mple 6- A. tablet containing. 0.486 gm. of ammoniuin chloride is coated, in any oonv'entional mannei, with cellulose acetate phthalate; the weight. of the coating being ab0ut"l% of'the weighto'fth'e] tablet. 'The thus coated tablet is then overcoated with glyceryl monostearate, the Weight of the coating being 5% of the weight-of the tablet.

Example? A tablet containing. 5 mg. amphetamine sul fate is first-coated with cellulose acetat e phthal ate, the weight. oi the coating-being 8% of the weightoi the tablet. The thus coated tabletEis then overcoated-with beeswax, the weight of the coating being-1% of the weight of the tablet;

Example 8 A tablet containing 0.65 gm.- ofammonium chloride is first coated with a -mix=ture corn-prisimg;-

. parts-byweight of-g1yceryl myristate and l5 parts-by-weight olcarnaub'aWax -the weight of the coating being 6%of the weightof: thetabl'etr' The tablet isthen-overcoated with cellulose-a'ce' tate phtha-late'; th weight of the coating=beirigv 6%of the" weight of thetabletw Example '9 A tahlet containing l0 mg. amphetamine-- sub--- fate is first coated with a mixture ceinprisingmlfi parts by weight I diglycol stearate' and ZSpar-ts-by weight-of beeswax, the weight of the coating be-- ing8%-'o'f theweightof thetablet; The-tablet" is then overcoated with cellulose acetate phthalate;.'the weight of the-coating being. 5%- of'the weight: otthe tablet.

Tests of tablets enteric coated according to the first example given" above show no penetrationby fluids of the stomach: for aperiod of ten" hours and disintegrationinabout one hour in -intesti Thus, according to this invention an enteric coating is provided which is insoluble and not dispersible in and impermeable by the fluids of the stomach and non-rupturable by agitation in the stomach, while, at the same time, it is readily dissipated by the fluids of the intestines.

In the following claims, the word soluble is intended to comprise also dispersible, digestible and emulsifiable.

What we claim and desire to protect by Letters Patent is:

1. A new article of manufacture comprising a medicament, and a coating comprising a layer of a cellulose derivative containing free carboxyl groups substantially insoluble in the stomach fluids and soluble in the intestinal fluids, and a layer of wax, said wax layer being characterized by the fact that its integrity will be maintained in the stomach and will be lost in the intestines and by the fact that it is not less than /2% by weight of the medicament.

2. A new article of manufacture comprising a medicament, a coating comprising a cellulose derivative containing free carboxyl groups substantially insoluble in the stomach fluids and soluble in the intestinal fluids, and an undercoating of wax, said wax coating bein characterized by the fact that its integrity will be maintained in the stomach and will be lost in the intestines and by the fact that it is not less than by weight of the medicament.

3. A new article of manufacture comprising a medicament, a coating comprising a cellulose derivative containing free carboxyl groups substantially insoluble in the stomach fluids and soluble in the intestinal fluids, and an overcoating of wax, said wax coating being characterized by the fact that its integrity will be maintained in the stomach and will be lost in the intestines and by the fact that it is not less than 1% by weight of the medicament.

4. A new article of manufacture comprising a medicament, and a coating comprising an inner layer of cellulose acetate phthalate and an outer layer of wax, said wax layer being characterized by the fact that its integrity will be maintained in 6 the stomach and will be lost in the intestines and by the fact that it is not less than 1% by weig t of the medicament.

5. A new article of manufacture comprising a medicament, and a coating comprising a layer of a cellulose derivative containing free carboxyl groups substantially insoluble in the stomach fluids and soluble in the intestinal fluids and a layer comprising in admixture a wax insoluble in the stomach fluids and soluble in the intestinal fluids and a wax insoluble in the gastro-inlayer of from 1% to 5% by weight of the medicament of a wax which is insoluble in the gastrointestinal tract, said layer of wax being the outer layer of the coating.

HAROLD A. CLYMER. DONALD R. MACDONNELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,196,768 Hiatt Apr. 9, 1940 2,410,417 Andersen Nov. 5, 1946 FOREIGN PATENTS Number Country Date 302,334 Germany Dec. 11, 1917 OTHER REFERENCES Thompson, Journal of the American Pharmaceutical Association, Sci. Ed., May 1945, page 135.

Bauer, Journal of the American Pharmaceutical Association, Scientific Edition, March 1948, vol. 37, pages 124 to 128. 

1. A NEW ARTICLE OF MANUFACTURE COMPRISING A MEDICAMENT, AND A COATING COMPRISING A LAYER OF A CELLULOSE DERIVATIVE CONTAINING FREE CARBOXYL GROUPS SUBSTANTIALLY INSOLUBLE IN THE STOMACH FLUIDS AND SOLUBLE IN THE INTESTINAL FLUIDS, AND A LAYER OF WAX, SAID WAX LAYER BEING CHARACTERIZED BY THE FACT THAT ITS INTEGRITY WILL BE MAINTAINED IN THE STOMACH AND WILL BE LOST IN TE INTESTINES AND BY THE FACT THAT IT IS NOT LESS THAN 1/2% BY WEIGHT OF THE MEDICAMENT. 